Differential delay line



1956 w. M. A. ANDERSEN 3,

DIFFERENTIAL DELAY LINE Filed Oct. 15, 1963 INVENTOR. WALTHER MA. ANDERSEN BYW ATTORNEYS United States Patent 3,227,970 DIFFERENTIAL DELAY LINE Walther M. A. Andersen, New Hartford, Conn., assignor to Andersen Laboratories Incorporated, West Hartford, Conn., a corporation of Connecticut Filed Get. 15, 1963, Ser. No. 316,220 Claims. (Cl. 33330) The present invention relates to adjustable delay lines, and more particularly to new and improved acoustical delay lines which provide for a differential delay in transmission time among a plurality of energy channels.

It is an object of the present invention to provide an adjustable delay line exhibiting not only time delays which possess a wide range of variation within individual channels but also preselected differential time delays among multiple channels.

Another object of the present invention is to provide an improved multiple channel delay line having a high rate of relative change of the time delays among individual channels for a given increment of adjustment.

A further object of this invention is to provide an improved ditferential ultrasonic delay line which is exceptionally compact for a given maximum of time delay and range of adjustment and is light in weight, rugged, reliable and accurate.

A still further object of the present invention is to provide a differential ultrasonic delay line having constant transmitted energy apertures thereby to provide exceptionally uniform response levels throughout the full range of adjustment.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth, and the scope of the application of which will be indicated in the appended claims.

In the drawing:

FIG. 1 is a perspective view of an embodiment of the invention; and

FIG. 2 is an exploded perspective view of the embodiment of FIG. 1, with portions thereof severed for purposes of illustration.

Referring now to the drawing in greater detail, the delay line 10 is generally shown as comprising three parallel-spaced elongated rails 12, 14 and 16 which preferably are fixed relative to each other and are made of material suitable for the transmission of acoustical signals such as quartz. The rails 12 and 14 are coupled by the coupling member 18 which permits acoustical transfer between the rails, while rails 14 and 16 are shown to be fixedly interconnected by reflector 20. At oppositely disposed ends of elongated rail 12 are located inclined faces 22 and 24 to which are attached quartz crystals or similar transducer members 26, 28, respectively. Rails 14 and 16 are each provided at a first end thereof with inclined faces 30, 32 to which are respectively fixed transducers 34 and 36 in a manner similar to crystal 26.

For purposes of illustration, a first energy channel is indicated by arrows 38, while a second energy channel is designated by arrows 40. Assuming transducer 26 to be an input transducer for the first channel, it is noted that the rail 12 provides an initial acoustical delay path whose signal may be coupled or transmitted to the terminal acoustical delay path of the same channel located in rail 14 by means of the ultrasonic bridge or coupling member 18. Output transducer 34 is positioned so as to receive the delayed signal of the first channel coming from rail 14. Similarly, if transducer 28 is assumed to be the input transducer for the second channel, rail 12 likewise provides an initial acoustical delay path for the second chan- "ice nel whose signal is coupled or transmitted to the terminal delay path in rails 14 and 16. The signals in both channels may be transferred or transmitted simultaneously by the ultrasonic coupling member 18 so that transducer 36 receives the delayed signal of the second channel at a delay time relative to the first channel, which delay depends on the relative length of the respective channel as determined by the position of coupling member 18. The terminal path of the second channel is shown as including both that portion of the second channel which progresses through rail 14 as well as the path indicated in rail 16. The two portions of the terminal path of the second channel are shown to be connected by reflector 20.

Rails 12, 14 and 16 are each shown as being provided with substantially flat longitudinal surfaces lying in a common plane and are identified respectively in FIG. 1 as 42, 44 and 46. Surfaces 42 and 44 may have thereon a thin layer or film of an unctuous material such as petroleum jelly or similar material which is viscous and flowable. As disclosed in United States Patent No. 2,659,053 issued to Sven J. Johnson, assigned to the assignee of the present invention, the use of an unctuous material on such surfaces facilitates the energy trans mission between rails such as 12 and a movable member such as coupling member 18 and minimizes distortion, reflection or attenuation.

Coupling member 18 is provided with a bottom surface which engages rails 12 and 14 and which may take the form of a fiat surface 48 overlying and engaging the coupling surfaces 42, 44 of the respective rails 12 and 14. The unctuous film on surfaces 42 and 44 not only facilitates the acoustical energy transmission but also lubricates coupling member 18 so that it moves smoothly and efiiciently to any desired position along surfaces 42 and 44. For example, as indicated in FIG. 1, coupling member 18 may be moved from the solid line position to the dotted line position and thereby differentially alter the time delays of both channels. It is readily apparent that a movement of coupling member 18 from the solid line position to the dotted line position will not only increase the time delay of the first channel 38 by increasing its path of travel but will, at the same time, decrease the effective path length of the second channel 40.

In order to transfer the energy obtained from impressing an electrical signal upon the respective input crystals or transducers 26 and 28 to the output crystals or transducers 34 and 36, coupling member 18 is provided with a plurality of angularly related specular or energy reflecting faces 50, 52, 54 and 56, each of which is shown to possess a constant effective area that is less than the areas of the transducers thereby to provide a constant aperture throughout the range of adjustment. Specular faces 50 and 52, located at one end of coupling member 18 are generally flat and are disposed at degrees to each other, and constitute energy reflective means for the second channel. They are tilted slightly toward coupling surfaces 42 and 44 and are generally at the same inclined angle to those surfaces as transducer 28 so as to be parallel thereto. The ultrasonic energy set up in transducer 28 will travel along the initial path of the second channel in rail 12 toward coupling surfaces 42, 48 and the unctuous material therebetween and will pass into coupling member 18 and impinge upon specular face 50 at an angle of substantially 45 degrees. Due to the fact that specular faces 50 and 52 are mutually perpendicular, it follows that energy reflecting from specular face 50 will also impinge upon face 52 at an angle of substantially 45 degrees. The angle is quite critical since it has been found that mode conversion takes place when the angle varies by more than a few minutes from 45 degrees. The signal is then reflected from face 52 and proceeds along the terminal portion of the second channel by passing out of coupling member 18 through coupling surfaces 44, 48 and the unctuous material thereon. The signal proceeds through rails 14 and 16, as indicated by arrows 40, by means of reflector fixed to the end of rails 14 and 16 opposite the first ends thereof. Reflector 20 provides reflecting surfaces 58 and 60 disposed at 90 degrees to each other, degrees to the energy impinging thereon and tilted slightly so as to be parallel to specular faces and 52. The signal impinging on surface 58 at 45 degrees thereto is reflected to surface and proceeds to transducer 36 by way of reflective surface 46 of rail 16.

Specular faces 54 and 56 of coupling member 18 constitute energy reflective means for the first channel and are also generally flat and disposed at 90 degrees to each other. Faces 54 and 56 are located at the end of coupling member 18 opposite the end containing specular faces 50 and 52. Faces 54 and 56 are also tilted slightly toward coupling surfaces 42 and 44 at generally the same angle as transducers 26 and 34 so as to be parallel to those surfaces. In a manner similar to that described for the second channel, the ultrasonic energy following the first channel will impinge upon face 54 at an angle of substantially 45 degrees and will be reflected to surface 56 whereon it will impinge at substantially the same angle before proceeding along the terminal path to output transducer 34.

Referring now particularly to the solid line position in FIG. 1, it can be readily seen that the first channel has its minimum effective length when the coupling member 18 is closest to first channel input transducer 26. By the same token, the second channel has its longest effective length when the coupling member is so positioned. However, as the coupling member 18 is moved toward the input end for the second channel the effective length of the first channel becomes greater while that of the second channel is diminished. Thus, the coupling member 18 can be moved, as for example to the dotted line position of FIG. 1, so as to increase the time delay of the first channel while simultaneously decreasing the time delay of the second channel. Further, according to the present invention, this is accomplished without undesirably affecting the transmitted signal. As is also apparent, the length of the respective channels is simultaneously altered a distance equal to twice the distance of movement of the coupling member 18. The movement of the coupling member 18 from the solid line position of FIG. 1 to the dotted line position not only varies the length of the respective channels but also diminishes, at an accelerated rate, the time differential between the two channels. Consequently, this invention provides an arrangement in which a differential delay in the transmission times through two channels of any system can be quickly and effectively generated in contrast to a single channel variable time delay scheme such as is exemplified by United States Patent No. 2,996,987, issued to Holden P. Wright and assigned to the assignee of the present invention.

It is, of course, within the scope of the present invention to vary the length of any portion of either channel so that, by relative movement of the coupling member with respect thereto, it would be possible not only to have both channels provide an identical delay in transmission time but also to have either channel provide a signal transmission time delay with respect to the other channel.

As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

I claim:

1. A multiple channel differential delay line comprising means providing first and second acoustical channels having energy input and output means for each of said channels, and a movable acoustical coupling element intersecting and relatively movable along said first and second acoustical channels for simultaneously oppositely 4 altering the delay times of said channels thereby to differentially control the delay times of the energy following the respective channels.

2. A differentially variable multiple channel delay line comprising means providing a first acoustical channel, means providing a second acoustical channel intersecting said first channel, each of said means having energy input and output means for each of said channels, a movable coupling element of acoustical delay material intersecting and moving along both of said channels and adjustable for simultaneously increasing and decreasing the effective lengths of the respective paths in an equal amount.

3. A differentially adjustable multiple channel ultrasonic delay line comprising means forming initial paths of first and second acoustical'delay channels having energy input means for each of said channels at the ends thereof, means forming terminal paths of said channels having energy output means for each of said paths at the ends thereof, a movable coupling member constructed of acoustical delay material intersecting and movable along said initial and terminal paths of said channels, said coupling member being provided with acoustically specular surfaces operative to transfer the propagated energy from the initial paths to the terminal paths of the respective channels without changing the mode of energy transmission, said coupling member being adjustable for simultaneously increasing the effective length of the first delay channel and decreasing the effective length of the second delay channel.

4. A differentially adjustable ultrasonic delay line comprising means forming initial paths of first and second acoustical delay channels; means forming terminal paths of said channels spaced from and generally parallel to said initial paths, said means forming initial and terminal paths each being provided with parallel substantially flat coupling surfaces; acoustical input transducers for each of said chanels aflixed to the ends of the means forming the initial paths and inclined slightly toward the coupling surface on said initial paths; output transducers for each of said channels affixed to the means forming the terminal paths and generally adjacent at least one of said input transducers; a movable coupling member constructed of acoustical delay material and having a surface overlying and engaging the parallel surfaces and intersecting the initial and terminal paths simultaneously, said coupling member being provided with energy reflective means for each channel operative to transfer the propagated energy from said initial paths to said terminal paths of the respective channels without changing the mode of energy transmission, said coupling member being adjustable for simultaneously and differentially changing the effective length of the first delay channel and the effective length of the second delay channel by equal amounts.

5. An ultrasonic delay line as set forth in claim 4 wherein each of said energy reflective means generally comprises two specular faces disposed at degrees to each other, each of said surfaces being further disposed 45 degrees to the direction of propagation of energy within said channels whereby the propagating energy is reflected from the initial paths to the terminal paths of the respective channels.

6. The delay line as set forth in claim 4 wherein said reflective means each have a constant effective area that is less than the areas of the transducers thereby to provide a delay line having a constant aperture throughout the range of adjustment.

7. An ultrasonic delay line for simultaneously and differentially adjusting a first and a second acoustical delay channel comprising a first solid elongated rail of acoustical delay material; a second solid elongated rail of acoustical material spaced from and parallel to said first rail, said rails having substantially flat parallel coupling surfaces formed thereon; transducer means located at opposite ends of said first elongated rail, each of said ends constituting a portion of only one of said first and second channels, said transducer means being inclined toward the coupling surface of said first rail; two additional transducer means each constituting a portion of only one of said channels, at least one of said additional transducers being located on said second rail and inclined toward the coupling surface of said second rail; and a coupling member constructed of acoustical delay material and having a surface overlying and engaging the coupling surfaces of said first and second rails, said coupling member being provided with first and second energy reflective means operative to transfer simultaneously the energy in said two distinct energy channels from one of said rails to the other of said rails, said coupling member being movable for simultaneously altering the lengths of said first and second channels in an equal and opposite amount thereby to difierentially control the delay times of the energy traversing the respective channels.

8. A delay line as set forth in claim 7 including a third solid elongated rail spaced from and generally parallel to said second rail and having a substantially flat reflective surface parallel with the coupling surfaces of said first and second rails; and a reflector fixedly secured to adjacent ends of said second and third rails and intersecting only one of said channels, said reflector comprised of two reflective surfaces disposed at 90 degrees to each other and 45 degrees to the energy channel intersected thereby.

9. The delay line of claim 7 wherein the energy reflecting means on said coupling member have a constant effective area that is less than the areas of the transducers thereby to provide a delay line having a constant aperture throughout the range of adjustment.

10. An ultrasonic delay line for simultaneously and differentially adjusting a first and a second acoustical delay channel comprising three parallel spaced rails of acoustical delay material, each of said rails having an elongated substantially flat coplanar surface; a first of said rails having two input transducers located on opposite ends thereof for setting up first and second acoustical energy signals; the remaining two rails having output transducers located on a first end thereof substantially parallel to one of said input transducers; a reflector joining said remaining two rails at the ends thereof opposite said first ends; said first rail and one of said remaining rails being acoustically joined by a slidable coupler having two acoustically specular faces disposed at one end thereof and two additional such faces disposed at the opposite end thereof; the first energy signal within said first channel impinging on the specular faces at one end of said coupler and the second energy signal Within said second chanel impinging on said opposite end of said coupler.

No references cited.

HERMAN KARL SAALBACI-I, Primary Examiner. 

1. A MULTIPLE CHANNEL DIFFERENTIAL DELAY LINE COMPRISING MEANS PROVIDING FIRST AND SECOND ACOUSTICAL CHANNELS HAVING ENERGY INPUT AND OUTPUT MEANS FOR EACH OF SAID CHANNELS, AND A MOVABLE ACOUSTICAL COUPLING ELEMENT INTERSECTING AND RELATIVELY MOVABLE ALONG SAID FIRST AND SECOND ACOUSTICAL CHANNELS FOR SIMULTANEOUSLY OPPOSITELY ALTERING THE DELAY TIMES OF SAID CHANNELS THEREBY TO DIFFERENTIALLY CONTROL THE DELAY TIMES OF THE ENERGY FOLLOWING THE RESPECTIVE CHANNELS. 